1. Field of the Invention
The present invention relates to a switching power-supply module in a DCxe2x80x94DC converter or suitable apparatus.
2. Description of the Related Art
FIG. 3 schematically shows an example of a switching power-supply module. This switching power-supply module 1 includes a substrate 2, a coil device 3, circuit components 4 other than the coil device 3, such as an IC chip, a capacitor element, and a semiconductor element, and a plurality of terminals 5.
In the switching power-supply module 1, a circuit pattern (not shown) is formed on the substrate 2, and the circuit components 4 are surface-mounted on one of or both of the front and back surfaces of the substrate 2 with solder. The circuit pattern, the circuit components 4, and the coil device 3 constitute a switching power-supply circuit in a DCxe2x80x94DC converter.
The coil device 3 is a transformer or an inductor which constitutes the switching power-supply circuit, and is produced by using the substrate 2. That is, the substrate 2 is provided with a coil pattern 6 which constitutes the coil device 3, and core-leg insertion holes 7 (7a, 7b, and 7c) formed in the substrate 2 adjacent to the coil pattern 6. Cores 8 are placed on both the front and back surfaces of the substrate 2, leg portions of the cores 8 are inserted in the core-leg insertion holes 7, and a portion of the coil pattern 6 is clamped by the cores 8 from both the front and back sides of the substrate 2, thereby constructing the coil device 3. In FIG. 3, a coupling member 9 combines and mounts a pair of cores 8 onto the substrate 2.
A plurality of terminals 5 are arranged at a fixed pitch in each of a pair of opposing edge portions of the substrate 2. The terminals 5 include a terminal functioning as an input terminal which supplies power from an external circuit to the switching power-supply circuit, a terminal functioning as an output terminal which directs the output of the switching power-supply circuit to the outside, and a terminal functioning as a control terminal which supplies a control signal for externally controlling the switching power-supply circuit.
On a mount board 10 on which such a switching power-supply module 1 is mounted, lands 11 are arranged so as to correspond to positions of the terminals 5. By solder-connecting the lands 11 and the leading ends of the corresponding terminals 5, the switching power-supply module 1 can be surface-mounted on a mount region Z of the mount board 10.
In a procedure for manufacturing such a switching power-supply module 1, first, a circuit pattern is formed on the substrate 2, and the coil device 3 and the circuit components 4 are mounted on the substrate 2. A plurality of terminals 5 are then arranged on the edge of the substrate 2. In this case, for example, a terminal-arranging member 15 shown in FIG. 4A is used. The terminal-arranging member 15 includes a plurality of terminals 5 arranged at a fixed pitch P, and allows the terminals 5 to be mounted together on the edge of the substrate 2.
FIG. 4B is a right-side view of the terminal-arranging member 15 shown in FIG. 4A. In the example shown in FIGS. 4A and 4B, a clip 16 is provided at one end of each terminal 5. The terminal 5 is mounted on the substrate 2 by clamping the substrate 2 by the clip 16 from both the front and back sides. After the terminals 5 are mounted on the substrate 2 by the clips 16, the terminal-arranging member 15 is cut at the base sides of the terminals 5 along the cutting line L so as to separate the terminals 5.
After the mounting of such terminals 5 is completed, the edge of the substrate 2 where the terminals 5 are arranged is soaked in molten solder 13 in a solder bath 12, as shown in FIG. 5. Solder thereby adheres, for example, around the clips 16 of the terminals 5. The terminals 5 and the substrate 2 are solder-connected by cooling the solder.
The switching power-supply module 1 can be produced through such a manufacturing procedure.
Such a switching power-supply module 1 has been required to be reduced in size. In order to meet the requirement, various techniques have been proposed. However, the switching power-supply module 1 is required to be further reduced in size, and a new technique is needed to meet this requirement.
In order to overcome the problems described above, preferred embodiments of the present invention provide a switching power-supply module that is easily reduced in size.
According to a preferred embodiment of the present invention, a switching power-supply module includes a substrate on which a switching power-supply circuit is provided, and a plurality of terminals arranged on an edge portion of the substrate, wherein a coil pattern is disposed on the substrate, a transformer or an inductor is mounted on the coil pattern with a core fitted in a hole formed in the substrate, the edge portion of the substrate on which the terminals are arranged is a prohibited component-mounting region where surface-mounting of a solder-connected component is prohibited, a portion of the coil pattern projects into the prohibited component-mounting region, and the terminals are arranged on the edge portion of the substrate so that they do not touch the coil pattern.
Preferably, the prohibited component-mounting region is soaked or dipped in molten solder in order to solder the terminals placed on the substrate.
Preferably, the terminals are arranged on the edge portion of the substrate at a fixed pitch so that a forming region of the coil pattern interrupts the arrangement of the terminals.
Preferably, a resist layer covers at least a portion of the coil pattern.
Conventionally, on the edge portion of the substrate on which the terminals are placed, surface-mounting of solder-connected components (components to be mounted on the substrate with solder) is prohibited. This is because such an edge portion having the terminals is sometimes soaked in molten solder in order to solder the terminals. If solder-connected components are surface-mounted in this region, solder between the solder-connected components and the substrate melts when soaked in molten solder, and the solder-connected components fall off the substrate. It has been generally considered prior to the development of the present invention that the prohibited component-mounting region is a dead space in which any component of the switching power-supply circuit cannot be formed or disposed.
When the switching power-supply circuit includes a transformer and an inductor, a coil pattern is sometimes provided on the substrate, and the transformer and the inductor are defined by the coil pattern. Since the coil pattern is a component of the circuit, it is arranged on the substrate so as not to touch the prohibited component-mounting region.
In contrast, the present inventor has discovered that the coil pattern is prevented from being damaged by molten solder, for example, by a resist layer formed thereon, and has made the preferred embodiments of the present invention which is superior enough to replace the conventional ideas and devices.
That is, in preferred embodiments of the present invention, a portion of the coil pattern is arranged so as to project into the prohibited component-mounting region, and a plurality of terminals are arranged on the edge portion of the substrate so that they do not touch the coil pattern. Since this characteristic structure allows a portion of the coil pattern to be located in the region which has been previously considered to be a dead space, it is possible to minimize the dead space, and to further reduce the size of the switching power-supply module.
Further elements, characteristics, features, and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.